The present invention relates to material handling and in particular to methods and apparatuses for conveying packages and a mechanism for controlling the location of packages on a conveyor.
Conventional conveyor systems convey large numbers of packages at high speed, especially in the parcel delivery industry wherein the packages are sorted according to the desired categories. The efficiency with which the packages are handled can be seriously diminished when a plurality of smaller packages, irregular sized or shaped items, or a mixture of oversized, large, and small articles pass together on the conveyors as a single unit.
Problems occur with scanning and separating packages and parcels which travel through the conveying system as an aggregate unit rather than in a single file and with oversize packages. Large packages hide small parcels and small side-by-side packages cause problems whenever they pass simultaneously through a scanner causing confusion and sorting problems. Moreover, packages such as bags or other flexible containers having the weight distributed unevenly, or where the width and length of the container are extreme, or where the container is soft or only partially full such as a floppy partially filled bag of mail tend to present sorting problems in that they do not move in predictable lateral patterns.
Typical conveyor systems for sorting parcels in typical applications comprise devices that take randomly arranged items and convert the random flow to a single file stream of items. The items are conveyed forward with both forward and lateral forces and aligned along one side. An ejector, ramp or other device can be placed after the aligned stream of items in order to remove items that did not make it all the way to the side wall on the aligned side to be separated laterally away from the primary stream of parcels. Typical configurations direct the laterally removed items and recirculate them back to the skewed roller section for another pass and opportunity to be aligned against the wall, to be passed through with the primary line of flow. Items are conveyed forward with both forward and lateral forces and aligned along one side.
Present technology works well for rigid parcels, like a box, but items that do not behave as a rigid item like flexible parcels or large bags containing several small items and oversized parcels are separated in accordance with their center of gravity and need to be removed from the parallel stream when the item is not aligned in single file.
Rearrangement of clusters of articles into a singulated single file is difficult to accomplish with packages having one dimension that is significantly greater than its other dimensions. If several packages having unequal loading, partially filled bags or boxes, or long and slender articles are conveyed side-by-side, conventional article singulation conveyors have difficulty separating side-by-side pairs into single file especially over a short distance and residence time. Occasionally instead of being positioned in single file, some of the packages may be conveyed abreast of one another, i.e., in side-by-side relationship traveling two abreast. The combined width of the two packages may present a problem at a downstream location in the conveyor system especially if one or both packages are oversize.
The need exists for a simple means of removing oversized items such as a shift and hold conveyor assembly for removal of oversized items which may be used as a module in a conveyor system or be used together with a singulator conveyor to organize packages having unequal weight, irregular dimensions, and off-set center of gravity.